Measurements of the variation in the inclination of structures are frequent and carried out especially in the case of the measurement of geophysical deformations, more specifically of seismic deformations. Such measurements are also performed to forestall a possible danger of collapse of buildings or of a part of the latter, or else to track the evolution of the storage of fluids in geological storage sites and the migration of these fluids into the permeable layer.
During an earthquake, in fault zones, the movement of geological faults occurs rapidly. The detection of these movements is easy. Between two earthquakes, deformations exist but are very small and very slow. Now, these deformations are coupled with seismic activity and the detection of these deformations is indispensable for understanding the mechanism of faults in the Earth's crust. Measurement instruments which are very precise and reliable over the long term must therefore be called upon.
At the present time very few devices capable of carrying out the measurement of these small deformations over the long term exist on the market. The known current devices are generally bubble inclinometers, such as for example the Lily borehole inclinometer from Applied Geomechanics (trademark), which allow the measurement of these deformations on the basis of the measurement of variations in inclination in boreholes sunk into the Earth's crust.